The peripheral nervous system (PNS) extends outside the central nervous system (CNS) and provides the functions of, amongst other things, bringing sensory information to the CNS and receiving motor commands from the CNS, coordinating body movements and controlling the involuntary muscles. Unlike the central nervous system, the PNS is not protected by bone and is therefore vulnerable to injuries.
Damage to nerves of the PNS can cause significant motor or sensory impairment. In particular, patients with acute peripheral nerve injury usually have nerve conduction defects that can manifest as motor impairment or sensory dysfunction. Depending on the severity of the injury and the nerve affected, a severed nerve may cause paralysis, partial loss of mobility of the affected limb and/or a loss of sensation. Nerve and muscle atrophy will follow if no sufficient recovery occurs or no timely treatment is provided. Similarly, crush damage to peripheral nerves can result in reduced motor or sensory performance.
Surgical intervention is required if there is to be any prospect of repairing severed peripheral nerves. One surgical technique for attempting growth of a peripheral nerve involves providing a scaffold, usually in the form of a conduit, at the site of the nerve damage, to facilitate and encourage the extension of regenerating axons. Specifically, the scaffold is selected to provide an environment that will encourage nerve growth so that nerve function can be returned. To date, success rates for peripheral nerve growth have been low and it is presently not possible to achieve the extent of peripheral nerve growth that would be required in order to repair many of the injuries experienced by peripheral nerves. It has been suggested [1] that polyhydroxybutyrate (PHB) can be used to make peripheral nerve growth conduits, but, again, only low levels of peripheral nerve growth have been reported and the problem of repairing substantial peripheral nerve damage remains.